Converting a horizontal dairy tank to HLT

[Sean W.]

I am considering converting a 500 gallon horizontal, insulated dairy tank to a HLT for our 10 barrel system. I was wondering if anyone had some ideas on exactly how to do this. Please see pictures, attached.

The tank has cooling jackets, but we will not have a steam boiler, so we would be looking at installing an electric heating element to heat the water. If anyone has brand recommendations or specs, that would help a lot. I was thinking, in order to avoid any cutting through the jacketed side of the tank, it makes sense to weld the heating element, as well as the temp probe, and auto on/off float switch, to one of the 2 lids.

I think I would install a recirculation / sprayball arm, possibly to go in the other lid. I would change out the bottom valve to a T.C. butterfly valve. I might also put in a sight tube, although we can always just look in the top or wait until water is coming out the top to know when it is full.

Only other thing I can think of is the inspection of the stainless steel on the dairy tank. I have been inside it, it looks great, no weird cracks or anything that looks remotely scary. But are there any particular warning signs I should look for before investing money into retrofitting this tank?

Thanks for the help,
Sean

[Starcat]

Some Considerations

Sean, such projects can work but need careful consideration at every design step.
Also the tank cooling jackets are not likely rated for steam even if you had it.

The BTU demand for an electric system must be somewhat calculated so you can arrive at the needed KW rating of your elements.
Also its better to have more than one element and have them staged when doing an arrangement like this.
That means a control array with contactors or a more sophisticated control system.
A multi stage contactor array is not hard to engineer or build for someone with commercial-industrial electrical experience.

You don't want your control sensor right by the elements. That will definitely not work out.

It would be better to have your elements at intervals and not in the manway. As thus, see what your KW rating is available in and go with FPT fittings and have them welded into the tank. There are outifts that make all kinds of custom styles of electric industrial elements in all manner of styles. MPT elements that screw into FPT fittings make sense.

You need a failsafe for low water cutoff and also high water cutoff, there are several ways to do this.
This has to be integrated into your control panel system. In this manner you run a fill solenoid.

[TGTimm]

I think you'll find that the horizontal tank is not very functional for an HLT. You must keep your elements submerged when heating, and a horizontal tank will have a higher percentage of its capacity left when the level gets down to the elements. Stratification will probably be a problem. More insulation for the entire tank will probably be needed. If the tank is already insulated with foam insulation (likely), you'll need to remove it and replace it with high-density fiberglass. Plastic foam insulation will not handle the heat of an HLT, and will produce some nasty gasses as it decomposes. If foam is enclosed between two jackets, the gas pressure might be high enough to rupture the thinner jacket.

I would consider using this tank to capture your castback cooling water, and get an upright tank for the HLT.

Our 10 bbl HLT uses 18X6kW home water-heater elements. We use the low-density style (Camco part # 02613), due to our high carbonate hardness. These elements last for many years if they don't get buried in sediment (keep then a ways off the bottom of the tank), and are not run dry (a level sensor that shuts the elements off in case of low water is cheap insurance). These two arrays (one of 12 elements, one of 6) can heat 10 bbl from 45F to 195F in about 20 minutes. The home water heater elements are much, much, cheaper that commercial types--each element is ~$20-30, whereas a Sussman 18kW 3P element (the equivalent of 3X6kW home elements) is over $500; doesn't last any longer or work any better.

Our heater arrays are 3P, 230V Delta. This simplifies the wiring considerably over a single-phase array (only one wire/element to pull, 3 elements/breaker). The elements screw into 1"-11 1/2 tpi FPT fittings (I cut 316L SS 3,000psi rated couplings in half to get two fittings/coupler--the 3,000 psi fittings have a thicker wall for the element gaskets to seat on) welded to a plate, which is welded to the tank. Be sure to have your electrician over-size the wiring--we used 6 Awg. Resistive heating elements generate lots of heat (kinda the idea), and big wires can handle the the heat.

Here's a pic of the 12 element array:



The deeper in your tank the elements are placed, the better for several reasons. As I mentioned above, heating elements will burn out INSTANTLY if they are run dry. With the elements near the bottom, you'll discourage the water from stratifying, which will be a problem with the horizontal tank anyway. Just keep them far enough off the bottom to prevent them from being buried in sediment, which will also burn them out. I'd look to weld an array of elements into each end of the tank, which might not be insulated.

Are you planning on making your heater a pressurized heater, or running it at ambient with a pump? The latter is much easier, cheaper, and safer. If you're making it a pressure vessel, you'll need to have any welds tested and certified. I'd stick with ambient pressure and an HL pump.

[Starcat]

Check

Timm, excellent point on the horizontal aspect with reference to electric elements.

[Sean W.]

Thanks for the advice guys. Kind of a bummer that the insulation is most likely not heat rated. That's something I didn't think of. I have some other potential places to put this tank in our system, and it probably makes sense to use it for something else if that's the case.